Rodents

Page Content

Rodents are widespread throughout Southland, with the exception of the Kiore which are restricted to Fiordland, Stewart Island/Rakiura and some offshore islands. The house mouse may be absent from Stewart Island/Rakiura.

What is it?

Norway rats are the largest of the three rat species and are found mainly in wet habitats and in association with human activity.

Ship rats are found in most habitats, especially native forests and are now the most abundant and widespread rat in Southland.

Kiore are the smallest and least common rat species in Southland and are restricted to remote parts of the region.

The house mouse is common throughout the region except Stewart Island.

What is the problem?

Rodents reach high numbers and have direct impacts on biodiversity, reducing forest regeneration by feeding on flowers, fruits, seeds and seedlings. They also prey on insects, lizards, birds and their eggs. Rodents can impact the economy of the region by feeding on crops, eating stored products and damaging buildings. They can be a nuisance to people around their properties and pose a potential risk to human health.

How to control it

Control methods

Example

Trapping

Best option inside houses and for small numbers of rodents. A range of kill traps are available commercially.

Poisoning

Best for controlling larger infestations of rodents. Poisons can be purchased from farm supply stores. Bait stations should be used for large-scale environmental control of rodents. Rodent blocks best for control in native forests.

Classification

Norway rats, Ship rats, Kiore and House mice are considered suppression animals on mainland Southland. They are too well established to eradicate from the mainland, so our aim is to suppress their numbers so that impacts on the community and the environment are minimised. Norway rat, Ship rats, Kiore and House mice are exclusion animals on offshore and inland islands. House mice are an exclusion animal on Stewart Island/Rakiura. Norway rats, Ship rats and Kiore are a suppression animal on Stewart Island/Rakiura.

Rules

No person shall release any rodent into the wild within Southland. No person shall take or transport within Southland, any rodent to any offshore island, any inland island or area enclosed by a pest exclusion fence. For a full explanation of the rules for rodents see the Regional Pest Management Strategy.

Monitoring

Environment Southland monitors rodent activity quarterly using tracking tunnels at the following locations:

The first four of the sites listed have pest control managed by community groups and the monitoring results provide helpful feedback on the success of their controls. The Lower Mataura covenants owned by Environment Southland offer a good opportunity to test new rodent control techniques and monitoring is used to provide feedback on these tests.